Point-of-care fluorescent immunoassay for identifying biomarkers in patient biofluid samples

Systems and methods for low-cost point-of-care immunoassay are provided. The system comprises an emitter, two optical interference filters, a microscope slide, a photodiode detector, a circuit, and a measuring unit. The detector is placed upon the second filter, the slide, the first filter, and then the emitter. The emitter comprises non-organic light emitting diodes (LEDs) or organic light emitting diodes (OLEDs) that emits light of a first color. The slide is spotted with biofluid from a patient. Biomarkers in the biofluid is bound with immobilized fluorophores that emit light of a second color when stimulated by the light of the first color. The first and second filters band-pass the light of the first and second colors, respectively. The detector detects light of the second color. The current outputted from the detector is converted into a relatively-large output voltage by a circuit. A measuring unit measures the ramp time of the output voltage. The ramp time is to be used to determine the concentration of the fluorophores, which in turn is related to the concentration of the biomarkers.